The present invention relates to a circuit for actuating one or more electric motors, especially the electric motors of an electronic typewriter. Such a typewriter has a platen roller, a carriage which is movable parallel to the platen roller and a printing device which is mounted on the carriage and which is operable to select the character to be printed. Movement of the carriage, selection of the character to be printed and rotation of the platen roller are produced by three electric direct current motors with which there are associated the same number of transducers which detect their rotary movement and generate corresponding electrical signals.
An arrangement for controlling the speed and positioning of an electric motor of a typewriter is known, wherein a microprocessor, on the basis of the amplitude of the rotary movement that the motor is to produce, generates logic signals which are suitably processed by an actuation circuit to accelerate and brake or short-circuit the motor. In that arrangement, for each unitary distance that the motor is to cover on the basis of a table of prerecorded times, the microprocessor determines a theoretical time for converging the respective distance and compares it to the actual time taken by the motor in order to determine if the motor is to be accelerated or braked or short-circuited. Such an arrangement is effective, but since the microprocessor also controls the specific printing and editing features of the typewriter its time response is rather low. This result is especially disadvantageous in view of the fact that the microprocessor must control all the motors of the typewriter.